Tuesday, July 24, 2007
In manufacturing a cylinder barrel the cast iron blanks are first bored with a multi-point tool then brought to their finished size with an abrasive hone. The last step is to scour the honed bore with a coarser, reciprocating hone operated at a fairly low speed. This produces the characteristic cross-hatching, the grooves of which hold a significant quantity of oil that facilitates the process of breaking-in the freshly assembled engine.
The grooves also hold a residue of carborundum, stripped from the coarse hone. These particles can produce vertical scoring on start-up, creating wounds in the cylinder wall that grow progressively worse over time. Although there are a number of high-tek ways to remove the residue (ultra-sound is one) but the cost of doing so can push the price of a set P&C's right out of the market-place.
Fortunately, there is an effective low-tek method developed in the early days of automotive maintenance. You simply scrub the bores of your newly honed cylinder with an abrasive cleanser. For the last seventy years or so Bon-Ami cleanser has been the preferred stuff but other cleansers containing pumice, chalk or diatomatious earth work equally well. These relatively mild abrasives break-down under pressure and are no threat to the innards of your engine. Alas, you can’t use any of the modern-day scouring powders which often contain such lovely stuff as powdered glass and chlorine bleach. Chlorine is about the last thing you want anywhere near cast iron and powdered glass, while it does a beautiful job of removing the porcelain from the kitchen sink, is almost as bad for your engine as carborundum.
There are two schools of thought on how to scrub your jugs. One sez the only proper way to do it is up & down, the way God intended. But there’s a few heathens who insist on doing it roundy-round, especially those who advocate the use of Lava soap rather than Bon-Ami. Others use Boraxo Powdered Hand Soap; a few mix their own formulations.
Personally, I’ve not noticed any difference at the finish line. In fact, the main difference is between those who do scrub their jugs versus those who don’t. The former make up a lot of the familiar faces in finish-line photos while the latter are rarely seen at all. Some (including me) will argue it isn’t the scrubbing but the overall attention to detail that is the key to a properly assembled engine. Scrubbing your jugs is just another of the many ‘unimportant’ details the newbies joke about and never do since it serves no purpose. According to them.
As to how to give your barrels a bath, the holes for the head-stays divides the barrel into quadrants. Put the barrel into your wash bucket, tub or whatever, submerged in water. Dampen your sponge, charge it with a couple of squeezes of Bon-Ami, 20-Mule Team or whatever, pick up the jug in one hand, the sponge in the other and give one quadrant twenty strokes. Dip, re-charge the sponge, rotate to the next quadrant and repeat. After doing all four, rinse the barrel and the sponge... and do it all over again. Four more times. Fig 1 shows the area set up for scrubbing jugs.
If you’re a Lava Man, same routine except you’re going roundy-round whilst everyone else is doing it up & down.
Expect it to take fifteen to twenty minutes per jug.
But before getting all wet & sweaty go find a big pot, fill it with water and set it to boil. If you’ve got a stove in your shop (I do!) things are a bit easier than if you have to work in the kitchen. Or the back yard. Working outside, the best boiler is probably a barbeque. And yes, you want the water boiling, or as close to it as you can get at your elevation.
You’ll also need a piece of stiff wire to fish the jugs out of the boiling water and a pad of newspaper or cardboard to sit them on after they are sprayed. As in WD-40. Because if you aren’t standing there Johnny-on-the-Spot with your can of WD-40 at the ready, your jugs are rust right before your eyes. And yes, WD-40 is okay for this job. In fact, that’s what the ‘WD’ stands for: Water Dispersant, formulation #40. Developed for Convair back in their Atlas missile days.
Ready to scrub? Then go to it.
After scrubbing a jug, take it over to the hot pot, hook the wire through a hole and slosh it in the boiling water. Do a good job of it; you want that jug to get hot. While it’s getting hot you’re grabbing a rag to use to hold on to the can of WD-40 (soapy hands, etc.).
Raise the hot, rinsed jug out of the water, orient it so the over-spray won’t kill anything and soak it down with WD-40. Let it drip a bit then sit on the drain pad, recover your wire and get busy with the next one.
Figure on spending an hour or more per set of jugs. And that doesn’t count the preparation & clean-up. (Hint: Doing more than one set of jugs at a time will reduce your overhead.) (Double Hint: Add another notch to the fin showing which set the jug belongs to.)
Despite conventional wisdom WD-40 is not a protective coating. It was - - and is - - a water dispersant and while handy for other things, protecting bare metal isn’t one of them. So make up a pad of paper toweling, soak it with motor oil and wipe down the bores of your scrubbed jugs. Careful! The last one out of the pot will be too hot too touch. Try doing a bit of clean-up first; give it a chance to cool down. Okay; now wipe them down and put them back into the box according to their notches/numbers. (Fig 3 up at the start of the article shows the scrubbed jugs cooling in the shade.)
PS -- Some one familiar with my shop wondered why most of the photos were taken in the patio.
I've got a nice shop with a lot of tools. A nice private shop. In this engine assembly series I'm sticking to basic methods that don't need a lot of tools. I no longer offer engines for sale. I don't encourage visitors, and there are things in my shop I prefer to share only with family & friends.
This will not effect the quality of the engine in any way. Indeed, the pictures are probably a more realistic representation of what the average builder is doing. -- rsh